There was a political bombshell yesterday in China. The country's ruling Communist Party announced an investigation into a former top official who's suspected of corruption. The nature of the charges against the ex-security czar are not yet clear, but he could be the highest-ranking official to face corruption charges since the beginning of communist rule.

NPR's Anthony Kuhn reports.

ANTHONY KUHN, BYLINE: For months, Zhou Yongkang was the name that could not be mentioned, even as his relatives and subordinates were detained and investigated. But with the silence broken, the official People's Daily newspaper said in an editorial today that Zhou's case sends a clear message - no Communist Party member is above the law. That's a powerful statement to make, in a country where for centuries, rulers were largely above the law.

Zhang Ming (ph), a historian at People's University in Beijing, says, that tradition and the structure of the party's power have mostly stayed the same since the death of Chairman Mao in 1976.

ZHANG MING: (Through translator) In the post-Mao era, there's been a consensus that political struggles should not get out of hand. People shouldn't get killed. Since 1989, they haven't touched anyone at the level of the Politburo Standing Committee.

KUHN: There are plenty of reasons why China's leadership would not want to prosecute one of its own. For one, it's an admission that the rot of corruption extends to the very top of the system. Also, Zhou was one of China's nine most powerful men on the Communist Party's Politburo Standing Committee until he retired two years ago. Qin Hui (ph), a historian at Beijing's Tsinghua University, notes that, as head of China's police and security apparatus, Zhou was in a good position to dig incriminating dirt on any political rival.

QIN HUI: (Through translator) I think a lot of people of qualms about taking down Zhou Yongkang. They are afraid he would become desperate and try to drag others down with him. Xi Jinping would not have taken Zhou out, unless he felt he posed a threat to him. But China's Party boss and president Xi Jinping, seems intent on outdoing his predecessors, both in wielding his own power and in raising China's standards of governance. His administration has investigated 25,000 officials for corruption in just the first half of this year, including dozens at and above the cabinet level.

KUHN: Again, historian Qin Hui.

HUI: (Chinese spoken)

KUHN: He's even talked about constraining official power inside the cage of institutions, he says. I think he's serious, but what he means is, constraining other people's power while he controls the cage.

Of course, no one can really be sure about Xi Jinping's motives. Independent commentator and former journalist Deng Yuwen, says, that what counts is what Xi is seen to be doing.

DENG YUWEN: (Through translator) Whether it's a political feud or an anti-graft campaign, it doesn't matter. As long as he takes down the Tiger, then the rules have been broken. So never mind what his motives are.

KUHN: Xi has pledged to go after both tigers and flies - in other words - both heavyweight politicians and lowly officials. Dong says, this has raised expectations of fairness and equality under the law. And that includes expectations that Zhou will eventually be given a fair and transparent public trial. Anthony Kuhn. NPR News, Beijing. Transcript provided by NPR, Copyright NPR.